1. Field of Invention
The field of the present invention is network devices that allow for data to be received and transmitted on a network. More specifically, the present invention is directed to network devices that may be chained together to provide higher port densities and to low-cost network devices. The present invention relates to a method and an apparatus for across-device communications. This across-device communication allows for the network devices to act as one switch assembly and allows for data to be received, examined and transmitted to the appropriate destinations.
2. Description of Related Art
Many types of network devices are necessary to allow a network to function properly. One such network device is commonly referred to as a switch. A switch is defined as a network component that receives incoming data, stores the data temporarily, and sends the data back out another port. The switch determines a destination address from the incoming data and sends the data to a port or ports associated with the destination address. In order to achieve higher port densities, multiple network devices or switches may be tied together. For example, suppose a particular chip housing the switch has an 8 fast Ethernet ports and 2 gigabit ports. In order to provide a switch assembly with a greater port density, perhaps having 16+4, or 24+6 or 36+8 port system, two, three or four chips, respectively, must be interconnected to provide such functionality. As such, many switches also have at least one expansion port so that multiple chips can be chained together.
One option that may be used for cross chip communication is using what is known as SerDes as the physical layer media. SerDes is a module that provides fast serial communication between two chips, where SerDes stands for serialization/deserialization. However, there are several problems associated with using SerDes to provide the cross chip communication required. First, when used with a standard interface, it is difficult to provide the required throughput to achieve the bandwidth needed for line speed switching. Second, because of the required inter packet gap (IPG), more channels of the SerDes must be devoted to inter-chip communication to achieve the required throughput.
Thus, there is a need for a mechanism in network devices that allows for across device communication that can be achieved through a relatively low cost solution. Additionally, while use of SerDes could provide a low cost solution, it was several drawbacks that do not allow for communication of the necessary speeds to be achieved through Serdes modules. Also, a protocol is needed to provide such across chip communication, such that the network devices can be interconnected and achieve the port density, without adding additional overhead.